Cleanup code using forward declarations.

Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.

share/qt/extract_strings_qt.py

@@ -57,7 +57,10 @@ child = Popen([XGETTEXT,'--output=-','-n','--keyword=_'] + files, stdout=PIPE)
 messages = parse_po(out) 
 
 f = open(OUT_CPP, 'w')
-f.write("""#include <QtGlobal>
+f.write("""
+
+#include <QtGlobal>
+
 // Automatically generated by extract_strings.py
 #ifdef __GNUC__
 #define UNUSED __attribute__((unused))
@@ -70,5 +73,5 @@ messages.sort(key=operator.itemgetter(0))
 for (msgid, msgstr) in messages:
     if msgid != EMPTY:
         f.write('QT_TRANSLATE_NOOP("bitcoin-core", %s),\n' % ('\n'.join(msgid)))
-f.write('};')
+f.write('};\n')
 f.close()